Conventionally, a cellulose-containing fabric has been treated with cellulase to impart desired properties to the fabric. For example, in the textile industry, a treatment with cellulase is carried out to improve the touch feel and appearance of a cellulose-containing fabric, or to impart a “stonewash” appearance to a colored cellulose-containing fabric, thereby providing the fabric with localized color change [patent reference 1].
Cellulases used for such uses include endoglucanases belonging to family 45, endoglucanases belonging to family 5, and endoglucanases belonging to family 12. It is normal in this technical field that these endoglucanases may be appropriately selected in accordance with their properties (for example, an optimum pH, an optimum temperature, an effect to improve the texture of a fabric, or an influence on fiber strength). Endoglucanases belonging to family 45 are mainly used under neutral conditions, endoglucanases belonging to family 12 are used under acidic conditions to neutral conditions, and endoglucanases belonging to family 5 are mainly used under acidic conditions. Examples of endoglucanases belonging to family 45 include a purified 43 kDa endoglucanase component derived from genus Humicola [patent reference 2], endoglucanase NCE5 derived from genus Humicola [patent reference 3], and endoglucanase RCE I derived from genus Rhizopus [patent reference 4].
Examples of endoglucanases belonging to family 5 include endoglucanase SCE3 derived from genus Trichoderma [patent reference 5]. Examples of endoglucanases belonging to family 12 include endoglucanase EG III derived from genus Trichoderma [non-patent reference 1] and endoglucanase FI-CMCase derived from genus Aspergillus [non-patent reference 2]. It is known that genus Penicillium produces endoglucanase having a molecular weight of 25 kDa [non-patent reference 3].
When these enzymes are used for fabric processing, reactions are generally carried out under optimum conditions. Optimum temperatures of these known enzymes are within a middle temperature area (for example, 40° C. to 60° C.), and optimum pHs thereof are around between an acidic condition and a neutral condition (for example, pH 4.0 to pH 8.0). In this technical field, there is no case of an enzyme having a low optimum temperature (such as lower than 40° C.) or a strongly acidic optimum pH (such as less than pH 4.0) being commonly used industrially. In industrial processing of cellulose-containing fabrics, a cellulase preparation is commonly provided as a preparation comprising a large amount of endoglucanase having a high activity. As a process for manufacturing such a preparation, processes of overexpressing a desired endoglucanase component having a high activity in host cells using genetic recombinant techniques are known [patent references 6, 7].
As preferable host cells used in these processes, there may be mentioned, for example, filamentous fungi belonging to Hyphomycetes, such as filamentous fungi belonging to genus Aspergillus, Humicola, or Trichoderma. When cellulase used in fabric processing under acidic or strongly acidic condition is produced, genus Trichoderma producing acidic cellulase is preferable as host cells, by comparison with genus Aspergillus or Humicola producing neutral cellulase, because a synergistic effect caused by cellulase derived from the host is expected. Particularly, in view of the industrial production of the enzyme, the filamentous fungi belonging to genus Trichoderma having a high productivity is most preferable [patent reference 8]. However, when a filamentous fungus belonging to genus Trichoderma is used to express a gene derived from a different species (i.e., exogenous gene), the expression is often inhibited because features in the nucleotide sequence of the gene (such as codon usage in the gene) are different. In this case, it is necessary to modify the exogenous gene. For example, when endoglucanase RCE I derived from genus Rhizopus belonging to Zygomycetes is overexpressed in Humicola insolens, the gene encoding RCE I should be optimized in accordance with the codon usage of the host cell [patent reference 4]. However, if such an optimization is carried out, it will be difficult to express an exogenous gene as much as endogenous genes. Further, even when the enzyme of interest is actually expressed and produced in a host, it is anticipated that the enzyme is digested with proteases or the like contained in a culture liquid during cultivation to obtain the enzyme as digested products or partial fragments.    [patent reference 1] European Patent No. 307,564    [patent reference 2] International Publication WO98/03640    [patent reference 3] International Publication WO01/090375    [patent reference 4] International Publication WO00/24879    [patent reference 5] International Publication WO98/54332    [patent reference 6] International Publication WO91/17243    [patent reference 7] International Publication WO98/03667    [patent reference 8] International Publication WO05/054475    [non-patent reference 1] Okada, H. et. al., “Appl. Environ. Microbiol”, 64, 1998, p. 555-563    [non-patent reference 2] Ooi, T. et. al., “Nucleic Acids Research”, 18, 1990, p. 5884    [non-patent reference 3] K. Mahalingeshwara et. al., “Carbohydrate Research” 190, 1989, p. 279-297